SMPS Limit-Cycle Oscillation Generation via Digital Transfer Function Alteration
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Solution Overview
Problem
Switch-mode power supplies (SMPSs) face challenges in determining optimal component parameters and compensation responses due to variations in storage element reactances and resistances, leading to conservative designs that increase costs and capacitance requirements, and disrupt output and input power supply characteristics.
Innovation Solution
A method and system that generate limit-cycle oscillations (LCOs) in SMPSs by temporarily altering the transfer function of digital elements in the control feedback loop, allowing for measurement of SMPS parameters and compensation values without disrupting the output or input of the power supply, using techniques such as altering ADC output codes or replacing digital elements with different transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conservative approach to compensation is taken to account for device-to-device variations and temperature effects, then reliability is improved, but capacitance requirements increase by at least 40% and costs increase
Solution Approach 1:
The patent changes the parameters of the compensator dynamically based on measured LCO characteristics. By measuring the actual LCO frequency and amplitude under specific test conditions, the system determines optimal compensator parameters (such as pole-zero locations) that are tailored to the specific device and operating conditions, replacing the need for conservative fixed parameters that required 40% larger capacitance.
Solution Approach 2:
The system performs self-characterization by automatically measuring its own LCO properties and using this information to optimize its compensation parameters. The power supply controller executes test sequences, measures the responses, and autonomously determines the optimal compensator settings without external intervention, enabling each device to be optimized for its specific characteristics rather than relying on conservative generic design margins.
2Manufacturing precision
If production tuning is performed to compensate for device variations, then manufacturing precision is improved, but device complexity and rejection rates increase
Solution Approach 1:
Instead of requiring external production tuning equipment and processes, the system performs its own characterization during manufacturing or initial operation. The power supply controller automatically executes test sequences that measure LCO characteristics and compute optimal compensator parameters, eliminating the need for separate production tuning equipment, reducing manufacturing complexity, and minimizing device rejection rates.
Solution Approach 2:
The patent replaces the mechanical/physical production tuning process with a digital computational approach. Rather than physically adjusting components or using complex production test equipment, the system uses digital signal processing to measure LCO characteristics and computationally determine optimal compensator parameters, simplifying the manufacturing process.
3Measurement precision
If the transfer function of a digital element is temporarily altered to generate LCO for measurement, then measurement precision is improved, but the power supply operation is disrupted
Solution Approach 1:
The system uses periodic test sequences where the transfer function is temporarily altered only during brief measurement intervals, then restored to normal operation. By conducting LCO measurements during designated test periods and returning to normal power supply operation afterward, the system achieves accurate parameter extraction while minimizing disruption to overall productivity.
Solution Approach 2:
The system performs LCO measurements and parameter extraction during initial characterization before normal operation begins, or during scheduled maintenance intervals. By completing the transfer function alteration and measurement activities beforehand, the system establishes accurate compensator parameters that optimize performance during subsequent continuous operation, minimizing disruption to productivity.
Data Source
AI summary
Limit-cycle oscillation (LCO) generation by altering a digital transfer function of a feedback loop element provides a controllable method and apparatus for generating LCOs within a switch-mode power supply (SMPS). Measurements of the LCO characteristics can then be used to determine characteristics of the SMPS and/or determine proper compensation schemes. At least a zero error code of the feedback loop element is removed, causing the control value to oscillate between at least two values. Additional codes may be progressively removed until an LCO is detected, in order to ensure LCO generation with minimum disruption of SMPS operation. An analog-to-digital converter (ADC) that converts an output voltage or current to a control value may be used to generate an LCO by removing one or more output codes to alter its transfer function. Alternatively, a quantization step of the pulse-width modulator or other modulator may be increased to temporarily cause LCOs.